The present invention relates to polyolefins, especially polypropylenes and their uses.
As known in the art, syndiotactic polymers have a unique stereochemical structure in which monomeric units having enantiomorphic configuration of the asymmetrical carbon atoms follow each other alternately and regularly in the macromolecular main chain. Syndiotactic polypropylene was first disclosed by Natta et al. in U.S. Pat. No. 3,258,455. The Natta group obtained syndiotactic polypropylene by using a catalyst prepared from titanium trichloride and diethyl aluminum monochloride. A later patent to Natta et al., U.S. Pat. No. 3,305,538, discloses the use of vanadium triacetylacetonate or halogenated vanadium compounds in combination with organic aluminum compounds for producing syndiotactic polypropylene.
U.S. Pat. No. 3,364,190 to Emrick discloses a catalyst system composed of finely divided titanium or vanadium trichloride, aluminum chloride, a trialkyl aluminum and a phosphorus-containing Lewis base as producing syndiotactic polypropylene. U.S. Pat. No. 4,892,851 disclosed a metallocene catalyst for producing highly crystalline syndiotactic polyolefins.
As disclosed in these patent references and as known in the art, the structure and properties of syndiotactic polypropylene differ significantly from those of isotactic polypropylene. The isotactic structure is typically described as having the methyl groups attached to the tertiary carbon atoms of successive monomeric units on the same side of a hypothetical plane through the main chain of the polymer, e.g., the methyl groups are all above or below the plane. Using the Fischer projection formula, the stereochemical sequence of isotactic polypropylene is described as follows: 
Another way of describing the structure is through the use of NMR. Bovey""s NMR nomenclature for an isotactic pentad is . . . mmmm . . . with each xe2x80x9cmxe2x80x9d representing a xe2x80x9cmesoxe2x80x9d dyad or successive methyl groups on the same side in the plane. As known in the art, any deviation or inversion in the structure of the chain lowers the degree of isotacticity and crystallinity of the polymer.
In contrast to the isotactic structure, syndiotactic polymers are those in which the methyl groups attached to the tertiary carbon atoms of successive monomeric units in the chain lie on alternate sides of the plane of the polymer. Using the Fischer projection formula, the structure of a syndiotactic polymer is designated as: 
In NMR nomenclature, this pentad is described as . . . rrrr . . . in which each xe2x80x9crxe2x80x9d represents a xe2x80x9cracemicxe2x80x9d dyad, i.e., successive methyl groups on alternate sides of the plane.
The percentage of r dyads in the chain determines the degree of syndiotacticity of the polymer. Syndiotactic polymers are crystalline and, like the isotactic polymers, are insoluble in xylene.
This crystallinity distinguishes both syndiotactic and isotactic polymers from an atactic polymer that is soluble in xylene. Atactic polymer exhibits no regular order of repeating unit configurations in the polymer chain and forms essentially a waxy product. While it is possible for a catalyst to produce all three types of polymer, it is desirable for a catalyst to produce predominantly syndiotactic or isotactic polymer with some atactic block fractions.
PCT/EP97/03649 (filed on 10th July 1997) of the present applicants describes a new syndiotactic/atactic block homopolyolefin and particularly a new syndiotactic/atactic block homopolypropylene. PCT/EP97/03649 also describes a catalyst and process for preparing syndiotactic/atactic block polyolefins, and more particularly syndiotactic/atactic block polypropylene. The catalyst and process can each be adapted to produce a polymer with differing syndio-/atactic block ratios.
The present invention provides use of syndiotactic/atactic block polypropylene whereby the properties thereof, especially the mechanical properties, are exploited. The syndiotactic/atactic block polypropylene has a combination of plastic properties conferred by the syndiotactic block and elastomeric properties conferred by the atactic block and may be regarded as a member of the xe2x80x9cthermoplastic elastomerxe2x80x9d family of polymers.
In one aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a modifier of a polyolefin, such as isotactic and/or copolymeric polypropylene and/or other polyolefins. The modified polyolefin or polypropylene formed thereby may be capable of moulding, for example by extrusion, injection or compression and can be used, for example, in high impact resistance applications such as automobile parts, electronic appliances, packaging and sports goods. Accordingly, there is further provided a high impact resistance polyolefin such as a polypropylene, comprising a dispersion of syndiotactic/atactic block polypropylene in a continuous phase comprising isotactic and/or copolymeric polypropylene. Preferably, the amount of syndiotactic/atactic block polypropylene is in the range 3 to 50%, preferably 5 to 15% by weight of the polypropylene. It is thought that the syndiotactic/atactic block polypropylene forms discrete dispersed particles in the continuous phase. In this way, the syndiotactic/atactic block polypropylene functions in the same way as rubber or elastomers in high impact polystyrene or as EPDM (ethylene propylene diene monomer such as a 1,4-hexadiene, or dicyclopentadiene or 5-ethylidene norbornene) particles in polypropylene.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a component in an adhesive composition. There is further provided an adhesive composition comprising a syndiotactic/atactic block polypropylene and at least one component selected from a wax, and a tackifying and/or reinforcing resin such as HERCOTAC 205 or MBG 212 (both from Hercules). Such adhesive compositions may be used, for example, in book binding applications. In such applications it is preferred that the components of the adhesive are selected so as to give a storage modulus Gxe2x80x2 in the range 3xc3x97106 to 5xc3x97107 and a soft phase glass transition temperature in the range 5 to 30xc2x0 C.
In a further aspect the present invention provides use of a syndiotactic/atactic block polypropylene as a component in a shock absorber. There is further provided a shock absorber comprising syndiotactic/atactic block polypropylene. In this application, the syndiotactic/atactic block polypropylene exhibits elasticity without rebound. It is found that rebound decreases as the molecular weight of the polypropylene increases. The syndiotactic/atactic block polypropylene appears to act in an analogous way to butyl rubber and could therefore be used in its place, wherever mechanical properties are concerned. The chemical properties of syndiotactic/atactic block polypropylene differ from those of butyl rubber. In particular, syndiotactic/atactic block polypropylene requires no further vulcanization during processing.
The shock absorber may further comprise other components known by those skilled in this art for use therein, such as carbon black, oils, inorganic fillers, organic fillers, other polymers and foaming and processing agents. Typical applications of such shock absorbers include footwear soles, silent-block (noise absorber or damper) and any absorber or damper required between vibrating parts.
Preferably, the shock absorber is for use at room temperature, for example 20xc2x0 C., and above.
In a further aspect, the present invention provides use of a syndiotactic/atactic block polypropylene as a component in a waterproof membrane. There is further provided a waterproof membrane comprising a sheet of syndiotactic/atactic block polypropylene modified with carbon black and/or a UV absorber and/or an antioxidant, and/or a weather resistance improver. Preferably, the amount of carbon black in the waterproof membrane is in the range 0.5% to 50%, more preferably 3% to 30%, depending on the grade of carbon black. It is found that carbon black dramatically improves the weathering resistance of the membrane. It is possible to extrude a very large sheet of the syndiotactic/atactic block polypropylene. In this way, the use of syndiotactic/atactic block polypropylene is similar to that of EPDM. Such sheets are useful in roofing applications.
In a further aspect, the present invention provides use of a syndiotactic/atactic block polypropylene in the form of a packaging film or as a component thereof. There is further provided a packaging material comprising a blown film of polypropylene comprising a syndiotactic/atactic block polypropylene. The polypropylene may comprise a blend of the syndiotactic/atactic block polypropylene. In one embodiment, the blown film is shrinkable. Good bubble stability is achievable in the production of blown films, particularly with a high molecular weight such as one above 180 kD. Shrinkable blown films are useful in bottle packaging, palette packaging and xe2x80x9cthrown-awayxe2x80x9d packaging (i.e. packaging for additives used in formulations in which the additives are added to the formulation together with the packaging itself so that the packaging forms part of the formulation).
In a further aspect, the present invention provides a drawn fibre, film or thread of syndiotactic/atactic block polypropylene. The fibre, film or thread may therefore comprise other polymers, usually blended with the syndiotactic/atactic block polypropylene, preferably a polyolefin such as isotactic polypropylene, copolymeric polypropylene, high density polyethylene and/or low density polyethylene.
In a further aspect, the present invention provides use of a syndiotactic/atactic block polypropylene as a continuous phase component in a shapable composition. There is further provided a shapable composition comprising a continuous phase of syndiotactic/atactic block polypropylene in which is dispersed isotactic polypropylene, copolymeric polypropylene or another polymer such as a polyolefin. Preferably, the shapable composition softens upon heating and becomes rigid upon subsequent cooling. The shapable composition is typically soft and may be gently warmed for shaping, for example by hand. The syndiotactic/atactic block polypropylene has a glass transition temperature close to 0xc2x0 C. When subsequently cooled, the composition becomes rigid owing to the presence of the isotactic polypropylene. The rigidity is due to crystallisation, whose speed is controlled by the amount of isotactic polypropylene, which is typically in the range 5 to 30% by weight of the composition. The shapable composition may be used in the production of a plaster cast or by craftsmen or artists.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a component in an acoustic absorbent material. There is further provided an acoustic absorbent material comprising a blend, laminate or coextrudate of syndiotactic/atactic block polypropylene with at least one of isotactic, syndiotactic or copolymeric polypropylene or another polymer such as a polyolefin. Each constituent of the acoustic absorbent material will absorb a part of the acoustic spectrum. The material may be useful in automobile interiors, for example.
In a further aspect the present invention provides a foam comprising syndiotactic/atactic block polypropylene.
The foam may be extruded, injection moulded or compressed. Long chain branching of the Syndiotactic/atactic block polypropylene affords a high melt strength which is required in the foam form, especially for a soft foam. The syndiotactic/atactic block polypropylene is preferably crosslinked, typically by addition of peroxide during foaming, or by curing with electron beam. Alternatively, the Syndiotactic/atactic block polypropylene may be blended with another compatible polymer such as a polyolefin so as to afford greater rigidity, depending on the respective amounts of the ingredients. Typically, the compatible polymer is present in an amount of from 0 to 99%, preferably 5 to 30%. Such foams may be used, for example, as thermal or acoustic insulating material or as shock absorbers.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene in a composition for moulding into a footwear component, usually in the sole. The invention further provides a composition for moulding into a footwear component, which comprises a syndiotactic/atactic block polypropylene optionally in combination with one or more additives known for this purpose, including plasticizers, polymeric fillers, mineral fillers and protective agents. Among these additives may be selected general purpose polystyrene, high impact polystyrene and/or appropriate oils. An appropriate choice of amount of syndiotactic/atactic block polypropylene and/or the selection of other components allows adjustment of the surface finish of the footwear component. In this way a matt or gloss finish may be achieved according to end use.
In a further aspect, the present invention provides a composition comprising a syndiotactic/atactic block polypropylene and a mineral filler, such as talcum, carbonate, silica and/or ash. Such mineral fillers may be used to improve the properties, such as weathering resistance, or reduce the price of the syndiotactic/atactic block polypropylene. Articles which may be made from such compositions include outdoor furniture, toys and sporting goods
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a compatibilizer, an emulgator or an emulsifier. Such use is particularly advantageous in plastics recycling or upgrading. The syndiotactic/atactic block polypropylene may be blended or mixed with plastics to obtain a mono-or biphasic system in which the syndiotactic/atactic block polypropylene may induce or create a continuous or dispersed phase depending on the processing conditions and the chemical and physical characteristics of the plastics.
In a further aspect, the present invention provides a coextrudate of syndiotactic/atactic block polypropylene with polypropylene and another polyolefin such as another polypropylene, a polypropylene copolymer, low density polyethylene, high density polypropylene or linear low density polyethylene. This is another example of the use of the Syndiotactic/atactic block polypropylene as a compatibilizer. For example, the syndiotactic/atactic block polypropylene may comprise an intermediate layer between a layer of a first polyolefin and a layer of a second poLyolefin, which layers may be incompatible with one another in the absence of the intermediate layer. For example, the first polyolefin may comprise syndiotactic polypropylene and the second polyolefin may comprise isotactic polypropylene.
The Syndiotactic/atactic block polypropylene may be present as a layer in a laminate between a layer of the polypropylene and the layer of the polyolefin.
In this embodiment, the syndiotactic polypropylene imparts dielectric properties, higher gloss and improved impact resistance whereas isotactic polypropylene imparts a higher crystallinity which gives the co-extrudate rigidity.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a viscosity improver, especially in a motor oil. There is further provided a motor oil which includes syndiotactic/atactic block polypropylene, typically in an amount of from 1 to 10% by weight of the material. Typically the viscosity index (VI) of the motor oil is in the range 100 to 150 (where VI=viscosity at 100xc2x0 F./viscosity at 210xc2x0 F.).
In a further aspect, the present invention provides use of cross-linked syndiotactic/atactic block polypropylene as a spilled oil absorber. In one embodiment there is provided a thermoplastic elastomer gel comprising cross-linked syndiotactic/atactic block polypropylene. There is further provided a spilled oil absorber comprising the thermoplastic elastomeric gel. A thermoplastic elastomeric gel has both hydrophobic and oleophilic properties. Syndiotactic/atactic block polypropylene is more soluble in solvent than either syndiotactic or isotactic polypropylene.
In a further aspect, the present invention provides a bitumen composition comprising a blend of bitumen with a syndiotactic/atactic block polypropylene, preferably wherein the amount of syndiotactic/atactic block polypropylene is less than 35% by weight of the composition, generally in the range 15 to 30% by weight.
The bitumen composition may be used in a waterproof membrane, a bridge membrane or in joints, for example, for buildings.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene in a composition or article substantially stable to gamma irradiation. There is further provided a composition or article substantially stable to gamma irradiation, which comprises syndiotactic/atactic block polypropylene optionally blended or co-extruded with a polyolefin such as polyethylene. Such compositions or articles include articles for sterilisation and medical articles such as blood pouches.
The catalyst useful in the production of the syndiotactic/atactic block polypropylene comprises a metallocene, i.e., a metal derivative of a cyclopentadiene, and an ionizing agent. The metallocene compound contains only one substituted cyclopentadienyl ring and is of the general formula:
Rxe2x80x3(C4Rxe2x80x2mC5C4Rxe2x80x2n)XMeQ
wherein X is an hetero-atom ligand with one or two lone pair electrons and selected from the elements of Group VA or VIA and is preferably nitrogen, phosphorus, oxygen or sulfur, which can be substituted or non-substituted; (C4Rmxe2x80x2C5C4Rnxe2x80x2) is a fluorenyl or a symmetrically substituted fluorenyl or cyclopentadienyl ring; Rxe2x80x2 is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each Rxe2x80x2 may be the same or different and m and n independently are 0, 1, 2, 3 or 4, with the proviso that the bilateraly symmetry is maintained; Rxe2x80x3 is a structural bridge between the X and (C4Rxe2x80x2mC5C4Rxe2x80x2n) ring to impart stereorigidity and, preferably is a silyl or a hydrocarbyl biradical having at least one silicon or carbon atom to form the bridge; Q is a hydrocarbyl radical, such as an alkyl, aryl, alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned in the Periodic Table of Elements; Me can be in any of its theoretically possible oxidation states. Preferred metals for the catalyst of the invention are Zr, Ti, Hf.
The term xe2x80x9csymmetricallyxe2x80x9d shall mean that the local bilateral symmetry of the active polymerization sites is essentially maintained.
The process for producing syndiotactic/atactic block polyolefins, particularly syndiotactic/atactic polypropylene comprises utilizing at least one of the catalysts described by the above formula and introducing the catalyst into a polymerization reaction zone containing an olefin monomer. In addition, a cocatalyst such as alumoxane may be introduced into the reaction zone. further, the catalyst may also be pre-polymerized prior to introducing it into the reaction zone and/or prior to the stabilization of reaction conditions in the reactor.
Metallocene catalysts are single site catalyst which, generally, produce polymer having narrow molecular weight distribution.
While the process is mainly directed to a-olefin homopolymerization, copolymerization with other olefins can be obtained.
The polypropylene may comprise alternating blocks of syndiotactic and atactic sequences, preferably long syndiotactic and short atactic sequences, most preferably comprising a fraction of syndiotactic triads (rr) of at least 70%. The polypropylene preferably has a molecular weight of at least 120 kD, more preferably at least 180 kD.